Japanese version
Complete the following achievements to unlock Xbox Live Gamerscore points:

3 Perfects in a row (30) - In battle, perform 3 Perfect ring maneuvers in a row.
500 Perfects (10) - In battle, perform 500 Perfect ring maneuvers.
Accumulate 1000000 damage (10) - In battle, deal 1,000,000 damage to enemies.
Around the world (10) - Visit all the unexplored areas in all the fields of the world.
Backyard - Light Class Master (10) - In the Backyard, achieve the battle bonus by clearing all hidden objectives in the Light Class.
Clear Disk 1 (125) - Finish playing through the end of Disc 1.
Clear Disk 2 (125) - Finish playing through the end of Disc 2.
Clear Disk 3 (125) - Finish playing through the end of Disc 3.
Clear Disk 4 (125) - Finish playing through the end of Disc 4.
Defeat 1000 enemies (10) - In battle, defeat 1,000 enemies.
Dream of a Thousand Years (20) - Gain access to all Dreams Of A Thousand Years.
First Dream of a Thousand Years (20) - Gain access to the first Dream Of A Thousand Years.
Learned all skills - Kaim (20) - Learn all available skills with Kaim.
Learned from a Skill Ring (30) - Immortals can learn skills through accessories.
Open all treasure chests (20) - Open all treasure chests in the field.

New Game+
Complete the game once, save after the credits, and then choose to continue from the saved file.

Refill health and SP
If you are stuck without much health or SP and are near a save spot, save and quit the game. When you load that saved game file you will have full health and SP.

Dragon Dragon
At the beginning of Disc 2, there is an island called Numara Atoll. The enemies on it are likely to be about level 50. You can actually defeat Hellshakers even at level 22. You should put on any skills that recover HP, MP, and GC when you defend. For example, put Cast Support on Kaim and have him use it on Ming at the start of the battle. For Seth, have Black Magic 3 and have her cast Poison. Have Mack have cast Dodger on Kaim. Have Jensen cast Seal on the monster. Have Ming cast Shine to blind the monster. At the end of the first turn the monster should be sealed, poisoned, and blinded. Have Jensen focus on healing. Ming should go back and forth between healing and curse or just heal. Once you at least put Dodger on Kaim and Seth at least once; have Mack use Wall. Have Kaim and Seth defend to raise GC every turn. This method does not always work, but after you succeed a few times you will begin to kill him regularly. After you defeat him, return to world map to heal then repeat the process as many times as desired. Note: If you hit the Hellshaker with Keolon spell or curse puts Keolon on him, he does 1 point of damage no matter what. However it will still require Poison, and Seal is definitely recommended. Also, if you hit him with Virus while poison is on he will take over 2,000 damage per turn.